Spikemuth is the only leg in the Gym Challenge without a stadium or a Power Spot to facilitate Dynamax. Instead, the player's Gym mission begins soon after passing the Pokémon Center, where they must fight a gauntlet of Team Yell Grunts, who reveal themselves to be the Gym Trainers of Spikemuth and formed Team Yell to support the Gym Leader's younger sister Marnie. Occasionally, a Kantonian Mr. Mime will block the path with an invisible wall, forcing the player to defeat a Grunt before they can proceed. The battle against the Gym Leader, Piers, takes place at the battlefield at the end of the town.
During the post-game, Marnie is revealed to have accepted her older brother's request to replace him as the Spikemuth Gym Leader, and can be challenged to an exhibition match at the Gym once per day.
Along the way to Wyndon, Piers revealed to Ash that Marnie had entered the World Coronation Series to attract more challengers to the Spikemuth Gym, which differed from other Galar Gyms in that it lacked a Power Spot and was thus unpopular. Although Ash and Marnie's battle ended in Ash's victory, Marnie's battle skills left such an impression on the audience that many people became interested in visiting Spikemuth, providing hope for revitalizing the town.
Spikemuth first appeared in PASS23, when Henry and Casey entered it. Soon after entering, a Golisopod and a Bronzong came after them, with their Trainers using communication devices attached on them to demand they hand over the data card that held information about their plans. However, when they found out that the data had been too corrupted by their earlier attack on the card for the remaining information to be any threat to them, they started to leave, only for Casey to demand they return the Pokémon they had stolen from her a year earlier in Slumbering Weald. When they refused, Casey attacked the Pokémon with her Raboot and destroyed the communication devices on them, forcing their Trainers, Sordward and Shielbert, to talk to them directly and thus unwittingly reveal their location to Piers's accurate ears. They revealed that they had stolen Casey's Pokémon due to her full strength posing a threat to their plan, as Zacian and Zamazenta had taken an interest in her and Henry.
Spikemuth was introduced as a Stadium card in the Pokémon Trading Card Game during the English Sword & Shield Series (the Japanese Sword & Shield Era). It was first released in the Japanese Infinity Zone expansion and the English Darkness Ablaze expansion, with artwork by 5ban Graphics. It makes the players put two damage counters on any Active Pokémon that moves to the Bench on their turn.
The Spikemuth Gym is the only known Gym to specialize in the Dark type.